Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Institute of Chemistry and Biochemistry, Laboratory of Protein Biochemistry, Freie Universität Berlin, Berlin, Germany.
Elife. 2019 Mar 13;8:e41299. doi: 10.7554/eLife.41299.
PSD-95 MAGUK family scaffold proteins are multi-domain organisers of synaptic transmission that contain three PDZ domains followed by an SH3-GK domain tandem. This domain architecture allows coordinated assembly of protein complexes composed of neurotransmitter receptors, synaptic adhesion molecules and downstream signalling effectors. Here we show that binding of monomeric CRIPT-derived PDZ ligands to the third PDZ domain of PSD-95 induces functional changes in the intramolecular SH3-GK domain assembly that influence subsequent homotypic and heterotypic complex formation. We identify PSD-95 interactors that differentially bind to the SH3-GK domain tandem depending on its conformational state. Among these interactors, we further establish the heterotrimeric G protein subunit Gnb5 as a PSD-95 complex partner at dendritic spines of rat hippocampal neurons. The PSD-95 GK domain binds to Gnb5, and this interaction is triggered by CRIPT-derived PDZ ligands binding to the third PDZ domain of PSD-95, unraveling a hierarchical binding mechanism of PSD-95 complex formation.
PSD-95 MAGUK 家族支架蛋白是突触传递的多结构域组织者，包含三个 PDZ 结构域，其后是一个 SH3-GK 结构域串联。这种结构域架构允许由神经递质受体、突触黏附分子和下游信号效应器组成的蛋白质复合物的协调组装。在这里，我们表明单体 CRIPT 衍生 PDZ 配体与 PSD-95 的第三个 PDZ 结构域的结合诱导分子内 SH3-GK 结构域组装的功能变化，从而影响随后的同源和异源复合物形成。我们确定了 PSD-95 的相互作用因子，这些因子根据其构象状态，差异地结合到 SH3-GK 结构域串联上。在这些相互作用因子中，我们进一步确定异三聚体 G 蛋白亚基 Gnb5 是大鼠海马神经元树突棘上 PSD-95 复合物的伙伴。PSD-95 的 GK 结构域与 Gnb5 结合，这种相互作用是由 CRIPT 衍生 PDZ 配体与 PSD-95 的第三个 PDZ 结构域结合触发的，揭示了 PSD-95 复合物形成的层次结合机制。
